The galvanic deposition of copper layers on different substrate surfaces has been known from prior art for a long time and has found its way into different areas of technology and is widely used. The deposition of copper layers is used both in the area of metalizing conductive substrates of various type, such as ferrous metals, steels or light metals, and in the area of metalizing non-conductive substrates, such as for example in the area of printed circuit board production or the production of wafers in semiconductor industry.
Typically, copper layers are deposited on different substrate surfaces from cyanide-containing electrolyte compositions by applying a suitable deposition current. The use of cyanide-containing copper electrolytes for the deposition of copper layers produces very good deposition results over a broad range of deposition current densities; however, it is environmentally unfriendly due to the cyanide content of the electrolytes. Besides high safety requirements for handling these electrolytes, costly wastewater treatment steps are necessary to avoid environmental pollution.
In prior art, attempts have been made to provide cyanide-free electrolyte compositions for the deposition of copper layers on substrate surfaces; however, all of them could not achieve the stability and range of application of cyanide-containing electrolyte compositions.
A further disadvantage of electrolyte compositions known from prior art is that they are either highly alkaline or strongly acidic, which means that in both cases special safety measures have to be observed when handling these electrolytes. In addition, the system components that come in contact with the respective electrolytes have to be made of highly corrosion-resistant materials.